Hydraulic Handbrake

[Ted_Mecheng]

Hi,

I am currently undertaking my 3rd year uni project. I plan to design a handbrake lever for fast road cars (road legal) and rally applications, which is capable of activating a hydraulic rear brake system. The lever will work on a pull release action similar to that found in a WRC car.

At present I’m researching information on existing hydraulic handbrakes and trying to establish the extent of the market for such a product.

If you could take the time to let me know if you or anyone you know would be interested in such a product, the type of application it would be used for or alternatively if you know anyone who already uses one. Also any information on the subject, books, websites etc it would be highly appreciated.

Thanks

[Tim Falce]

Welcome to ten-tenths Ted
A hydraulic hand brake it wouldn't be road legal for the UK. I need one and there are plenty out there that fit my needs, I am just too tight to buy one so I will continue leaving it in gear and keep a wheel wedge handy.

[tone83]

I dont believe the market is there for you since anyone into rallying will either fabricate their own cheaply or get a proper "works" upgrade. You would have to make it very cheap and univeral for all cars plus UK rally cars require a mechanical backup further complicating things.

what do you mean fast road use? i dont like the idea of encouraging people who cant drive anyway to operate their handbrake to assist cornering. That is not very sensible is it.

Did you know that a drum brake actually offers greater mechanical advantage. It is just the heat dissipation properties that lets it down on a rally stage.

[Ted_Mecheng]

Thanks for your input Falcemob. One of the aims of the project it to make the hydraulic handbrake system adhere to road safety legislation.

[Al Weyman]

I have one in my Camaro to comply with CTCRC rules, if you have ever seen an original foot operated 'handbrake' in one of these old cars you would know why apart from the fact I fitted BMW front discs to the rear. I bought it from Demon Tweeks, bit pricey but nice bit of kit. I can't see one being street legal as it is surely meant as an emergency brake as well as a parking brake if the hydraulic system failed and if it failed on the rear brakes then the handbrake simply would not work.

[Ted_Mecheng]

Thanks for the reply Al Weyman. To overcome the problem of hydraulic failure, a secondary cable system will be incorporated into the system.

[graham bahr]

due to a recent change in the law a hydralic handbrake CAN be legal for road use, however its hydralic circuit would have to be totally independant of the normal hydralic braking system, so if you had a seperate master cylinder and slave cylinders to opperate the handbrake that would be ok.

on a slightly different angle the new shape Vw passat has an electic handbrake, operated by a dash borad switch, and doesn't have any sort of handbrake lever at all

[ss_collins]

An old road rallying trick on a mechanical handbrake is simply to tape over the ratchet button - giving you much quicker on and off usage.. not really relevant but a nice story from the RCE office

[GordonG]

Or it's quite simple to make a 'fly off' handbrake (instead of taping over the button). IIRC you effectively swap the location of the rod from the push button and the return spring, and you end up with a ratchet that is only engaged when you push the button. If you just pull the lever and release the handbrake goes on and off. To park you pull and press the button at the same time.

V funny watching someone unititiated trying to release the handbrake as they yank on the lever while pressing the button. To release you just yank the lever leaving the button alone.

G

[BertMk2]

Originally Posted by ss_collins

An old road rallying trick on a mechanical handbrake is simply to tape over the ratchet button - giving you much quicker on and off usage.. not really relevant but a nice story from the RCE office

On our rally car we push the button in and then stick a screw through a pre-drilled hole to keep it in. Works fine if we remember to put the screw in before the first stage

[greenamex2]

graham - Have you got any more info on the law change.

I have the usual kit car solution/problem of a mechanical kart spot caliper and it sucks.

Going hydraulic would solve that problem and the fact that there are at least twelve immovable objects in the way of my handbrake cable routing. And it keeps freezing up in the winter, I usually park it with the handbrake off and a couple of bricks behind the wheels, it's OK, will only hit a Mondeo if it rolls back.

Ted_Mecheng - If you are quick you could have a customer! As a pointer, to be sold to the kit car market it would have to be able to be activated by ANY handbrake lever which means some kind of univeral bolt on design.

If your not quick AND the law HAS changed then I'll probably beat you to it ;-)

[graham bahr]

the main problem as far as the law goes with hydralic handbrakes was that they were not a totally seperate from teh foot brake.

re the law, find a clued up current MOT tester, due a change of job i havn't tested for 3 years so i have only heard a bit on the grapevine

[Dave Brand]

Originally Posted by graham bahr

re the law, find a clued up current MOT tester, due a change of job i havn't tested for 3 years so i have only heard a bit on the grapevine

A quick Yahoo search found the following, from the MoT testers' manual:

" Hydraulic parking brakes as a sole means of operation are not acceptable on vehicles first used on or after 1 January 1968. However, they may be used to assist the application or release of a mechanical brake."

[phoenix]

In my experience, the problem with a hydraulic handbrake, apart from the legalities on a car that has to be used on the road, is that they are useless as a parking brake; the pressure in the system bleeds away it seems, so if you leave the car parked at the top of a hil for a number of hours you will return to find it at the bottom!

When operated to aid cornering, as in rallying, they are fantastic at locking the wheels.

There is also a limited choice of calipers available that have a cable operated system as well as the hydraulic operation. If you have a cable system fitted too, getting the cable tension 'just right' so as not to interfere with the hydraulic operation, but work in the event of failure - and as an effective parking brake - is a real problem. Separate, cable operated parking brake calipers is the only satisfactory system I have found, but I have also found that you need two handbrake levers to operate them independantly.

[Al Weyman]

I use my hydraulc handbrake on the Camaro when I trailer it and the last time was for about 7 hours and it was still on firm.

[greenamex2]

I use a line lock for a handbrake on my car. It works fine as long as the brakes are stone cold.

Try and use it even half an hour after a session and the car will trundle off on a little journey all by itself in a very short space of time.

[Anuauto]

The most famous case was Jim McRae sitting in a cafe during Cyprus Rally practice and seeing his parked Nissan 240RS move off down the hill.
As has been hinted in earlier posts, the reality is that to get most hydraulic handbrakes to work properly, the additional cable system that makes it UK road legal has to be adjusted to be ineffective.
I was recently appalled to see a young impecunious driver spend significant money on an "off the shelf" hydraulic handbrake system rather than buy the m/cylinder and bracket most people use to make their own. I hope this was no more than an isolated aberation and the art of amateur self-preparation is not dying! - only if it is do you have a market.
Personally, on a rally car that had to use the homologated rear drums, I found negligible difference between what force I could apply with cable or hydraulic handbrake, even after 20 miles of stage.

[Al Weyman]

I was recently appalled to see a young impecunious driver spend significant money on an "off the shelf" hydraulic handbrake system rather than buy the m/cylinder and bracket

Was'nt me honest (I'm in my late 50's)

Seriously the reason I put one on the Camaro is the original is a foot operated affair and there was not enouh clearance on the transmission tunnel to move it there.

I I use a line lock for a handbrake on my car. It works fine as long as the brakes are stone cold.

Try and use it even half an hour after a session and the car will trundle off on a little journey all by itself in a very short space of time.

Maybe it is because i use that ridiculously expensive Castrol SRF fluid which is now what £60 plus vat a litre (or 1/2 litre!) from DT's.

[dtype38]

Hi Ted,

From the posts above there seems to be agreement that for a road car (in the UK anyway) the handbrake needs to be an independent system even if it acts on the same calipers as the footbrake. There seems also to be some doubt about using a hydraulic system as a parking brake because of possible loss of pressure, and also that its very difficult to adjust a dual cable/hydraulic system unless they are on separate calipers.

Just a suggestion, but it might be productive to look at designing a mechanism by which a single handbrake lever can be used to pressurise the hydraulic calipers for "flyoff" operation, or used to lock on a standard cable system for use as a parking brake. Something along the lines of a two position press button on the end, or a simple twist grip to swap between functions. If you could make it as a kit to retrofit existing cars then there may be a market for something for the track day, club rallying or "Max Power" markets.

[greenamex2]

I can only afford AP 500.

[dtype38]

I use SRF but don't pay nearly that for it! Last bottle I got was something like £48 inc vat. from my local friendly parts supplier (and yes that was for 1 litre). Sounds like you should shop around there Al.

[graham bahr]

Originally Posted by Denis Bassom

I can only afford AP 500.

after boiling problems despite its massive cost i went over to AP600, but when i built my new car i used race brake fluid from motal, which is miles cheaper and seems just as good, dunno where you'd get it as i get mine from Andy wickens or AW64 as he's known on here, might be worth a PM to him

[Dave Brand]

Originally Posted by phoenix

In my experience, the problem with a hydraulic handbrake, apart from the legalities on a car that has to be used on the road, is that they are useless as a parking brake; the pressure in the system bleeds away it seems, so if you leave the car parked at the top of a hil for a number of hours you will return to find it at the bottom!

Not necessarily the fault of the hydraulics - the same thing can happen with mechanically-operated handbrakes on discs (don't ask me how I know!). The problem is that if the handbrake is applied with the discs hot clamping pressure will be lost as the disc cools & contracts; with a drum, it's just the opposite, one of the reason why manufacturers like Mercedes, Volvo, Jaguar etc., use 'top hat' rear discs with a drum parking brake in the centre of the disc.

[Al Weyman]

I can only afford AP 500

Hey Dennis in these big heavy cars I was finding I was getting terminal brake fade at the end of a straight like Revett or Thruxton, some guy put me on to the SRF stuff and I can guarantee it was an instant cure and I will not risk anything else as even at 60 quid a litre it is cheap insurance.

Who is your supplier Dtype, I am sure it would be OK to name them as it is relevant to the post.

[dtype38]

I use Classic Spares Ltd (Jaguar Spare Parts Dealer) of Waltham Abbey, N. London. 01992 716236. They use it for racing their Jaguar XJS and do a good price for other racers. To be honest the price seems to go up and down a bit, which may depend on their supply price or maybe just on how well they did at their last race meeting, but they're good blokes. Worth a try. :-)